NON-ISOLATED DC/DC CONVERTERS
2.4 Vdc - 5.5 Vdc Input, 0.6 Vdc - 3.63 Vdc /6 A Outputs
January 13, 2011
Bel Power, Inc. , a subsidiary of Bel Fuse, Inc.
Tunable LoopTM
The SLIN-06F2Ax modules have a new feature that optimizes transient response of the module called Tunable
LoopTM.
External capacitors are usually added to the output of the module for two reasons: to reduce output ripple and
noise and to reduce output voltage deviations from the steady-state value in the presence of dynamic load
current changes. Adding external capacitance however affects the voltage control loop of the module, typically
causing the loop to slow down with sluggish response. Larger values of external capacitance could also cause
the module to become unstable.
The Tunable LoopTM allows the user to externally adjust the voltage control loop to match the filter network
connected to the output of the module. The Tunable LoopTM is implemented by connecting a series R-C
between the SENSE and TRIM pins of the module, as shown below. This R-C allows the user to externally
adjust the voltage loop feedback compensation of the module.
VOUT
SENSE
RTUNE
C O
MODULE
CTUNE
TRIM
RTrim
GND
Circuit diagram showing connection of RTUNE and CTUNE to tune the control loop of the module
Recommended values of RTUNE and CTUNE for different output capacitor combinations are given in Tables 2, 3, 4
and 5. Tables 2 and 4 shows the recommended values of RTUNE and CTUNE for different values of ceramic output
capacitors up to 940uF that might be needed for an application to meet output ripple and noise requirements.
Selecting RTUNE and CTUNE according to Tables 3 or 5 will ensure stable operation of the module.
In applications with tight output voltage limits in the presence of dynamic current loading, additional output
capacitance will be required. Tables 3 and 5 list recommended values of RTUNE and CTUNE in order to meet 2%
output voltage deviation limits for some common output voltages in the presence of a 3A to 6A step change
(50% of full load), with an input voltage of 5Vin and 3.3Vin respectively.
Please contact Bel Power technical representative to obtain more details of this feature as well as for guidelines
on how to select the right value of external R-C to tune the module for best transient performance and stable
operation for other output capacitance values or input voltages other than 5V.
Bel Fuse Inc. 206 Van Vorst Street, Jersey City, NJ 07302 • Tel 201-432-0463 • Fax 201-432-9542 • www.belfuse.com
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BEL [ BEL FUSE INC. ]
